Vanda roxburghii: an experimental evaluation of antinociceptive properties of a traditional epiphytic medicinal orchid in animal models

BACKGROUND: Ethnopharmacological approach has explored several leads from plant sources to identify potential new drugs for various diseases including pain. Vanda roxburghii R. Br., an epiphytic orchid is widely distributed throughout Bangladesh. The root of this plant has a folkloric reputation to treat inflammations, fever, dyspepsia, bronchitis, hiccough, piles, snake bites, and diseases of the nervous system. In this study therefore, we aimed to investigate antinociceptive and cytotoxic properties of the extracts from the root of V. roxburghii. METHODS: Dried powder of aerial root of V. roxburghii was extracted with methanol (VRM) and the resultant was fractionated into petroleum ether (VRP), chloroform (VRC), ethyl acetate (VRE), and residual aqueous fraction (VRA). The antinociceptive effect of the extracts was evaluated in mice using acetic acid-induced writhing, formalin injection, and hot plate tests. The brine shrimp lethality bioassay in vitro was used to evaluate cytotoxic activity of the plant extracts. RESULTS: In the acetic acid-induced writhing test, mice treated with different fractions (12.5, 25, and 50 mg/kg, i.p.) exhibited reduced number of writhing. Amongst, VRE showed the highest activity at all three concentrations (43.65, 71.34, and 80.23 %, respectively) in a dose-dependent manner. Secondly, VRC (12.5, 25, and 50 mg/kg, i.p.) displayed the highest reduction of paw licking time in mice during the first phase of the formalin test (by 15.00, 37.05, and 56.44 %, respectively) as well as during the second phase of the test (by 20.55, 49.08, and 59.81 %, respectively). In hot plate test, VRE treatment at doses of 25 and 50 mg/kg both increased the highest latency time after 30 min. All fractions showed lower cytotoxicity compared with the standard drug vincristine sulfate in the brine shrimp bioassay. CONCLUSION: Overall studies suggest that the root of V. roxburghii is effective as a potent analgesic with lower toxicity. Our findings support previous claims of traditional uses of V. roxburghii in different inflammatory disorders.